I don't have a navi on mine but I have seen several posts with problem similar to yours (another common problem). I haven't read them with much attention to detail but the fix had something to do with unhooking the battery for a period of time and rehooking it to allow the system to reset. The only other thing I could think of is your battery is too low. Do a search on this issue and you will find lots of info from previous posts.

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2010 Lexus RX350 still new
2003 BMW X5 3.0i w/sport package w/68K miles. (gone Thank God!)
2002 Dodge Ram 2500 4X4 cummins diesel w/198K miles, custom repo truck
2009 Scion tC w/46K miles
2007 Suzuki SV650 custom streetfighter
2000 Lexus GS400 w/165K miles